Electrical instrument for measuring, indicating, and other purposes



Jan. 6 1931. w. M. THORNTON ELECTRICAL INSTRUMENT FOR MEASURING, INDIGATING, AND OTHER PURPOSES .Filed April 13. 192B Patented Jan. 6, 1931 r I H g I ffUNIT-ED STATES; PATENT OFFICE WI'LLIAM .ri ivnnL krrro'nnroiiri onn'nWcAsTLE-uromTY E; menu l i u m's rnuiunn'r iters eame, InnIoA'rme, Ann orrnnn runrosns I .1 I J sweeten n ;agar 13' a ma s reg te in Great Britain 1 75,1927; l

v I This invention relates to electrical instru' tery and galvanometer joined across oppomer ts for measur-ing, indicating and 'othersitep'oints in the usual fashion. Adjacent purposes, and is based upon the discovery by tothe heateris-an electrode preferably insu-,-' the present applicant that, -heated conlated as described andconnected when the ssductor is placed in an alternating electro- .v g i rnatin to one end of a-trans- 6 static field, the conductor is cooledand that formergwinding and the other end ofsuchthe amount of such cooling isa measure of j' winding is earthed and connected to -the the intensity of the field. This effect is junction ottheflh'eatedconductor with the probably due to the movement of electri adjacent arm of the bridge. The-galva- 1e "cally-charged molecules of air at the surface.- nQmeter may be calibrated to read directly in of the'heatedconductor, andsuch movement voltages; r may 7 bereferred to as an ionic wind. 'Ifthe electric characteristics of the heated Thisfcoolingefiect also takes place when the conductor are known theinstrument maybe electrostatic field is unidirectional although used to 'measu're'watts by, for instance; first 15 in that case such efiect is mostapparent at using it as a volt meter as above mentioned extra high voltages. g I and then by inserting the heated conductorso *In its-broad aspect theinvention'comprises that it forms directly or indirectly-part of an electrical instrument having acon'ductor the circuit in which'the power is to be'meas heated preferablyelectrically and-joperating ured, the cur'rent'may be measured by the I by reasQnbf the-cooling effect upon theheat- Ychange' of resistance in the conductor, the 7 ed'fconductor of anelectrostatic field either electrostatic field'beingcut 0ft. he product I unidirectional-or alternating in which'it is willthen' give the Watts. I

-placed.- I I On alternating current circuitsit is found The cooling efiectproduces a change in the thatbelow a certainfrequency the cooling resistance of thefheated conductor and such efi ect of the ionic wind depends on the frechange is indicated or measuredlby any suitf quency of the alternating electrostatic 'field able arrangement, such as a Vheatstone and thus by keeping the voltage constant'thebridge or potentiometer. Preferably the} instrument-may be used to measure freheated conductoris' of a materialwhich has quency. It follows that in any instance if '3OI. a high'rate of change of-resistance with tem'- the resistance of thecircuit is known or can perature and it is shielded from air currents be measured, then I having determined the as, forinstance; by enclosing it ina glass ves-' frequency; the inductance or capacity in the sel which may befilled with air or gas at any circuit can be found. desired pressure. [I j 1 As previously mentioned, the heated con- 35 The t d Conductor y Itself o m 0119 ductor may be enclosed: in, for instance, a f electrode of the e c r a field it my glass vessel and it is found that the cooling interposed i u field between eiiectfof the electrostaticlield varies at'any P n n e f In elther case .tfhe heat rate over .a considerable range with the presed conductqr Preferably practlciuy at sure insuch vessel. "The instrument may i Pi n t t d at h1g1} therefore be used to measure gaseous pres tential insulated in solid or othelilr dli-elfectric sures V which forms an enclosure or s eati or it: 1 I and renders the portion adjacent to the heat d. msflmment fim i y' er and other low potentialparts inaccessible. f {LP usemm m mVO The applications of 'aninstrument 'acco'rd- 1 hlgh hlgh Voltage? as. 1 96 I ing to'this invention are numerous and the 'vlouslymentlonedv 9F at hlghipotentlal. following are given by wayof exa l need be handled or accessibleduring the use 'When the instrument is to'be used a lt of the instrument. Moreover the galvanommeter the heated conductor inayconstitute etergornother mstrumentand the vWheatone arm of a VVheatstone bridge with a .batstone bridge or. like arrangement .to which I i l section showing the essential parts of one practical formof an electrical instrument according to thisv invention,

Figure 2 is aidiagram showing the instrument in a circuit suitable for making-various electrical measurements, and

' Figures 3, 4: and 5show diagrammatically alternativeways inwhich the parts of the instrumentmay bear-ranged.

With reierencefirst to Figure 1 the high tension electrode is in the form of a conduct- 1 ingrod A contained'in ail-insulating sheath 7 B which covers it except for a knob or terminal at the upper end to which connection 'may. be made. This sheathed electrode is sup ortiedon a hollow insulator C which is prac. tice may be ofconsiderably greater relative length than is shown inthe figure. This hol low insulator C ismounted upon a base D and its lower portion forms a chamber con- .itaining a; conductor E adapted to be heated;

This conductor is. shown asa small filament sealed within a bulb andhaving its ends con- IlGClSGClgtO terminals Fen the base.

' voltage.

' trode A the conductor E is heated say to a dicates how the instrument maybe used for making electrical measurements, for example a .measurement of alternating' current The high tension electrode A is joined through a switch L to one end of thesecondary winding of a transformer G supplying current to a load represented at M connected to earthby a switch L in the position shown ii -full lines, The conductor E forms onearm of a Wheatstone bridge of which the re sistancejs H and the variable resistance H constitute the other, arms. A battery J and a. galvanometer K are joined inv the circuit as showmand the conductor E is earthed.

Supposing the arrangement to be such that when no voltage is app-lied to the elecdull red and the galvanometer reads zero, then when voltage is applied to A the conductor E. is cooled and the amount of such cooling will be indicated by a reading on' the'galv'anometer which may be calibrated to read voltages; Obviously the same result may be obtained by calibrating the variable resistance and adjusting that to bring the galvanometer reading back to zero.

If the switches L and L be moved into the.

position shownin dotted lines the electrode A'is disconnected and the heated conductor Ethrown into the load circuit. The load current maythen'be measured on the bridge and the product of that reading with the voltage read when the high tension circuit is connected to the electrode A will give the'volt-amperes orkilovolt-amperes of the circuit. I

When the voltage is unidirectional or the load known to be non-inductive the instrument can be used in this Way as a watt meter.

slio'wnior example in Figureiiwherethe heated conductor E ,hason each sideof it an electrode A connectedto the secondary.

with the, heated; conductor between two elec-,

voltages, as for instance in connection with SYllChIODlZlIlg dpelalllOns.

. lnesome cases the end of a high tension .A'somewhat similar arrangement, i. e. one" transformer I i trodes, but withf the electrodes of the same polarity and connected ,to separate sources of high voltage, may be used for comparing. such cable may itself-"form the electrode as in i A Figure .5 where A is the conductor ofsuch The, circuit diagram forming Figure 2 ina cable andaAf -its insulation. The end of the cable is. sealed into an insulating con- 7 supported in an insulator such as'the insulatorC'ofFigure 1., l 7 The dimensionsof the heated conductor.

length may be-a few millimetres andthesize '100 7 may be quite small; m nany. instances ts and sha'pe'of its enclosing bulb or chamber.

may vary to suit requirements; Wheiifthe air or gas within the bulb is at otherthan.

varied to suit the. voltage which is to be applied to the instrumentQ-The, volume of. the enclosed space within thebulb or other containing chamber should be sufficient-to give the desired cooling efiect dueto the move-. ment of ionized gas butsmall enough to mini ously-the chamber at the-bottom of the in-f sulator C in Figure 1 might be made so as to exclude outside influences onthe heated conductor, and if desired could otherwise made gas -tight.

c .105 atmospheric pressure thatpressure may. be.

be sealed orv 7 What I claim'as my invention and desireto secure by Letters Patent is H 1. An electrical instrument having a heated conductor in an electrostatic field and operating through the cooling effect of thatfield upon the heated conductor. I

2. In anielectrical instrument,-the combination of meansfor producing' an electrostatic field, a conductor in said field, and. means for measuring the coolingefiect of v effect of said electrostatic field. p

I 4. In an electrical instrument, the 'combi-- nation of means forproduc'ing an electrostatic field, a conductor insaid field, means forheating said conductorelectrically, and

means for measuring the change of resistance fv said field upon said conductor.

3, In an electricalinstrument, the combinat on of means for producing an electro-* static field, a conductor in said field, means for heating said conductor electrically, and

means for measuring the change of resistance of the heatedconduct'o'rdue to the cooling of the heated conductor Vdue'to the cooling effect of said electrostatic field in terms of the Voltage producing said field.

5. In an electrical instrument for rm easuring high voltages, the combination of an in-' sulating support, an electrode in said support adapted to be joined to one pole of a sourceof high voltage, a conductor'in proximity to said electrode,vmeans for heating said conductor by passing a; currentthrough it, 1 a and meansfor measuring the change of resistance in'said heated conductor due to the cooling efiect of the electrostatic field m, duced by the application of thevoltage'to said electrode. 7 1

i 6. In an electrical instrument for measuringhigh voltages, the combination ofaninsulating support,.aneleotrode in said'support adapted to be joined tofone pole of a source of high voltage, a conductor in proximity to said electrode, means forheating said conductor by passinga current through it, said conductor being connected to the. other (earthed) pole of the source of high voltage, and means for measuring the change of resistance in said heated conductor due to the cooling effect of the electrostatic field produced by theapplication of the voltage to said electrode.

7. In an electrical instrument for measuring high voltages, the combination of an insulating support, an electrode enclosed in solid di-electric material and held in said support, a source of high voltage having one pole connected to said electrode, a conductor in proximity to said electrode, a bulb enclosing said conductor, means for heating said conductor by passing a current through it,

said conductor being connected to theother (earthed) pole of the source of high voltage,

and means for measuring the cooling effect on the conductor of the electrostatic field produced by the high voltage.

WILLIAM MUNDELL THORNTON."

In testimony whereof I have signed name to thisrspecification. 

